Clarification on JFET

I have read this following statement about n channel JFET that depletion region is wider near the top of both p - type materials. what is the exact reason for this? and why such description is not provided for BJT, because even in BJT we have P-N junction?

For any JFET the depletion region is always even until and unless the source voltage is different from the drain voltage. When there is a voltage b/w source and drain, Vgs is different from Vgd and the width of the depletion layer depends on Vgs or Vgd.

In BJT the voltage across the depletion region does not vary regionally regardless of the bias at the terminals.